The subject matter disclosed herein relates to the art of hydrogen cooled generators and, more particularly, to a lubricant drain system for a hydrogen cooled generator.
Hydrogen cooled generators include a seal oil or lubricant drain system that includes a detraining tank. The detraining tank allows any entrained hydrogen to escape from the lubricant. After the hydrogen is removed, the lubricant is re-introduced to the generator. In operation, the lubricant flows along rotating components of the generator and picks up hydrogen before passing into the detraining tank. In the detraining tank, the hydrogen escapes or rises from the lubricant. The lubricant accumulates and eventually flows over a standpipe and passes towards a recycling tank. Before reaching the recycling tank, the lubricant passes through a float trap. During normal operating conditions, when lubricant pressure is above 15 psi, the float trap prevents any hydrogen that may pass with the lubricant over the standpipe from passing to the recycling tank.
During start up periods, when lubricant pressure is below 5 psi, the float trap does not function properly. During such times, a manual override system is employed. More specifically, during start up, or other periods of low operating pressure, an operator must manually operate a valve that isolates the lubricant from the recycling tank. The valve includes a sight glass that allows the operator to monitor lubricant flow. When the operator sees hydrogen (in the form of bubbles or foam) in the lubricant, the valve is adjusted to hold a level of lubricant in the sight glass. In addition to requiring manual operation, the above system allows lubricant having relatively high hydrogen levels to pass to the recycling tank. That is, while the float valve prevents gaseous hydrogen from entering the recycling tank, some hydrogen gas remains entrained in the hydrogen flowing over the standpipe. As the lubricant entering the standpipe is in contact with the hydrogen gas in the detraining tank, hydrogen levels in the lubricant remain high.